Magnetic ranging refers to well positioning that provides relative direction and distance of one well with respect to another. Several technologies for ranging from a ranging well to a remote casing in a target well are based upon launching an alternating current at a known frequency from a power supply at the earth's surface down the casing of the target well in order to generate a magnetic field radiated from the target well casing. A sensor in the ranging well may detect the magnetic field and, thus, be able to determine a distance and direction to the target well. Sensor measurement error may reduce the accuracy of the ranging operation.